Method and system for analyzing overhead line geometries

ABSTRACT

Methods and systems are provided for characterizing an overhead line. A radar signal is propagated in a region that includes at least a portion of the overhead line and a reference object, which may, for example, be a ground surface, growth over a ground surface, or another overhead line. A reflected radar signal is received from the overhead line and the reference object. A determination is made of a geometric relationship between the overhead line and the reference object, such as by determining a minimal separation between the overhead line and the reference object.

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part application ofapplication Ser. No. 09/745,329, entitled “RADAR CROSS-SECTIONMEASUREMENT SYSTEM FOR ANALYSIS OF ELECTRICALLY INSULATIVE STRUCTURES,”filed Dec. 20, 2000 by Gilbert F. Miceli and Michael Parisi (“the '329application”), the entire disclosure of which is incorporated herein byreference for all purposes. The '329 application is itself acontinuation-in-part application of Pat. No. 6,246,355, entitled “RADARCROSS-SECTION MEASUREMENT SYSTEM FOR ANALYSIS OF WOODEN STRUCTURES,”filed Oct. 7, 2000 by Gilbert F. Miceli and Michael Parisi (“the '355patent”), the entire disclosure of which is incorporated herein byreference in its entirety for all purposes. Both the '329 applicationand the '355 patent claim priority of Prov. Appl. No. 60/171,548, filedDec. 22, 1999 and of Prov. Appl. No. 60/191,444, filed Mar. 23, 2000,the entire disclosures of both of which are incorporated herein byreference for all purposes.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a method and system foranalyzing overhead-line arrangements with radar.

[0003] Overhead-line arrangements such as used for electricaltransmission or distribution lines include two principal components: thelines themselves, which may include conductors and/or static lines, anda mechanism for supporting the lines overhead. In some instances, thesupporting mechanism uses spaced wooden poles. The power-utility-systeminfrastructure alone in North America includes approximately 150,000,000wooden pole structures used to support overhead lines. A similarly largenumber of wooden poles are additionally used by the telecommunicationsindustry. There are a numerous aspects of this infrastructure that arerequired to conform with various specifications and which are subject toperiodic assessment for compliance with those specifications.

[0004] For example, while wood remains valuable as a material forconstructing power and telecommunications poles because of its costeffectiveness and reasonable durability, they are, nevertheless, subjectto deterioration over time. This deterioration arises not only fromclimatic effects, but also from biological and mechanical assaults.Biological deterioration may result from the activity of decay fungi,wood-boring insects, or birds. Woodpeckers have been known to borevertical tunnels in wooden poles greater than twelve feet in length.Mechanical damage can result from such things as vehicular collisions orshotgun impacts. Consequently, each wooden pole in the system must beinspected periodically and a determination made whether to replace thepole based on the strength of the pole. Typically, poles are inspectedon a 5-9 year cycle.

[0005] Various methods currently exist for evaluating pole strength,generally requiring direct physical contact with the pole. Such methodsrely primarily on sampling techniques in which the strength of the poleis deduced from an assessment of its characteristics at the sampledpoints. Such sampling is typically performed in the region of the poleeasily accessible by a technician, i.e. between about six feet above theground to about two feet below the ground, so that only about 10% of thepole is even within the sampling region. Crossarms, which are positionednear the tops of the poles, are rarely examined for deterioration.Current methods also tend to include significant reliance on thequalitative assessment of the technician examining the pole. Individualvisits to every pole to perform the inspection additionally result insubstantial costs for maintaining the pole infrastructures.

[0006] In addition to the functional integrity of the utility pole beingdependent on the structural soundness of the wooden pole and crossarmstructures, it may also depend on the condition of other insulative polestructures. For example, many utility poles are equipped with“insulators,” which are knobs that are affixed to the poles, usually onthe crossarms, and are used to support the utility lines. The insulatorsmay be fabricated of appropriate insulative material, such as rubber,fiberglass, ceramic, or porcelain. The insulators are also exposed toweather and biological deterioration that may adversely affect theirperformance. In some cases, cracks may form in the insulators and laterbe filled with water or metal. The change in electrical character mayresult in flashover, which may trip circuitry and in some cases cause afire that burns the wooden crossarm, or causes even greater damage.

[0007] Furthermore, a number of aspects of how the infrastructure may beused depend specifically on the geometry of the overhead lines. Forexample, one parameter that is particularly relevant when the overheadlines comprise bare overhead conductor lines is the line sag, whichcorresponds to the minimum separation between the overhead line and theground surface. If the distance between the line and the ground is toosmall, there is a danger of having a change of phase to ground, i.e. ofproducing arcing between the conductor line and the ground. Adetermination of an acceptable geometry, including the distance betweenthe ground and the line, depends on a number of factors, includingenvironmental factors such as temperature and operational factors suchas the load to be carried by the line. Moreover, the line sag maypotentially differ throughout the infrastructure depending on how thelines were hung and environmental factors, among other factors.

[0008] There is accordingly a need in the art for improved methods andsystems for analyzing overhead-line arrangements, including the abilityto evaluate the integrity of insulative structures and to define thegeometry of the overhead-line arrangement.

BRIEF SUMMARY OF THE INVENTION

[0009] Thus, embodiments of the invention are directed to a method andsystem for analyzing insulative structures. In certain embodiments, awooden structure, such as a utility or telecommunications pole, isanalyzed, while in other embodiments the invention is more generallyapplicable to other insulative components of structures.

[0010] In embodiments directed to the analysis of a wooden structure, alocation for the wooden structure is identified. A first radar signal ispropagated towards the wooden structure with a radar antenna while theradar antenna is motion along a navigation path in the vicinity of thewooden structure. A reflected radar signal is received from the woodenstructure, from which a determination is made whether the woodenstructure contains a structural anomaly. The wooden structure may beidentified by imaging the wooden structure, such as with a chargecoupled device or infrared camera. In certain embodiments, longitude andlatitude positions for the wooden structure are ascertained with aglobal positioning system. The location of the wooden structure may alsobe identified by reflecting a laser signal from it.

[0011] In various embodiments, a second radar signal modulated inaccordance with a pulse compression scheme is propagated towards thewooden structure. The first and second radar signals may be provided bythe same radar subsystem or by separate radar subsystems in differentembodiments. The determination of whether the wooden structure containsa structural anomaly may be made in one embodiment from data extractedfrom the reflected radar signal by calculating a density distributionfor the wooden structure. The calculated density distribution may beused to designate closed-volume regions within the wooden structurehaving a density less than a threshold density relative to a meandensity for the structure thereby identifying them as possiblestructural anomalies.

[0012] Other embodiments of the invention are directed to identifying ananomaly in an insulative component of a structure. In such embodiments,a location for the structure and a position for the insulative componentrelative to the structure are identified. A first radar signal ispropagated towards the insulative component with a radar antenna whilethe radar antenna is in motion along a navigation path in the vicinityof the structure. A reflected radar signal in received, from which it isdetermined whether the insulative component contains the anomaly.Various aspects of the invention used for the analysis of woodenstructures may also be incorporated in the identification of anomaliesin insulative components. In particular, propagating a second radarsignal modulated in accordance with a pulse compression scheme may beperformed such that the reflected radar signal includes signalcomponents originating from both the first and second radar signals.

[0013] In a specific application, these techniques are used forcharacterizing an overhead line. A radar signal is propagated in aregion that includes at least a portion of the overhead line and areference object, which may, for example, be a ground surface, growthover a ground surface, or another overhead line. A reflected radarsignal is received from the overhead line and the reference object. Adetermination is made of a geometric relationship between the overheadline and the reference object, such as by determining a minimalseparation between the overhead line and the reference object. Such amethod may be performed for any type of overhead line, including aconductor line, an electrical transmission line, and an electricaldistribution line. In some embodiments, such a geometrical analysis ofthe overhead line may be combined with identifying a structural anomalyin a support structure, particularly when the support structure is usedto support the overhead line.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The patent or application file contains at least one drawingexecuted in color. Copies of this patent or patent applicationpublication with color drawings will be provided by the Office uponrequest and payment of the necessary fee.

[0015] These and other embodiments of the present invention, as well asits advantages and features are described in more detail in conjunctionwith the text below and the attached figures, in which similar referencenumerals are used throughout the several drawings to refer to likeelements. Various components of the same type may be distinguished byfollowing the reference label with a hyphen and a second label thatdistinguishes among the components.

[0016]FIG. 1(a) is a block diagram showing the relationship betweenvarious elements of the system in one embodiment of the invention;

[0017]FIG. 1(b) is a perspective drawing illustrating some insulativestructures that may be analyzed with embodiments of the invention;

[0018] FIGS. 1(c), 1(d), 1(e), and 1(f) are schematic diagramsillustrating aspects of overhead-line geometries that may be analyzedwith embodiments of the invention;

[0019]FIG. 2 is a schematic diagram of one possible navigational paththat may be taken by the inspection vehicle when taking radarcross-section measurements of poles: part (a) shows a top view of thenavigational path and part (b) shows a side view of the navigationalpath;

[0020]FIG. 3 illustrates one configuration that may be used to equip anavigation vehicle to operate in accordance with an embodiment of theinvention;

[0021]FIG. 4 is a block diagram showing the relationship between varioussubsystem elements used in analyzing the insulative structures;

[0022]FIG. 5 is a schematic diagram showing the interaction of varioussensor signals with poles: part (a) shows a top view and part (b) showsa side view;

[0023]FIG. 6 is a representation of a cylindrical coordinate system;

[0024]FIG. 7 is a block diagram showing the analysis of collected data;

[0025]FIG. 8 is a schematic diagram of theinsulative-material-penetrating aspects of the radar analysis;

[0026]FIG. 9 is an example of a pole inspection report that may beprovided in accordance with embodiments of the invention; and

[0027]FIG. 10A provides an example of a radar image that identifies astructural weakness in a utility pole; and

[0028]FIG. 10B provides an example of a radar image that shows thegeometric arrangement of a set of overhead lines.

DETAILED DESCRIPTION OF THE INVENTION

[0029] 1. Overview

[0030] Embodiments of the invention include a radar measurement systemfor the analysis of overhead-line arrangements such as may be used forutility and telecommunications applications. The term “radar” refersgenerally to the use of electromagnetic radiation having a frequency inthe radio or microwave part of the electromagnetic spectrum, i.e.between about 50 MHz and 100 GHz. The overhead-line arrangements mayinclude support structures for supporting the overhead lines. In someembodiments, the support structures may have electrically insulativecomponents, such as where utility and telecommunications poles thatinclude wooden and other insulating components are used. In accordancewith one embodiment, a vehicle is operated in the vicinity of a portionof the overhead-line arrangement to be examined, systematically makingappropriate radar measurements of the support structures and lines. Inone embodiment, the vehicle is a land-based vehicle such as a truck,while in other embodiments, the vehicle is an airborne vehicle such as ahelicopter or other aircraft. The airborne vehicle may be preferred incircumstances where the portion of the arrangement to be examined is noteasily accessible by land, while the land-based vehicle may be preferredin circumstances where airspace restrictions limit access by air. Themeasurements are used by a computational analysis system to determinethe existence and location of any anomalies within any of the examinedpoles. A report of the results is prepared and forwarded to a client.

[0031] The overall structure of one such system is illustrated in FIG.1(a) in the form of a block diagram showing in particular the flow ofdata through the system. The system functions centrally with adispatcher 100 who is responsible for coordination of various otheraspects of the system. In operation, a client 105 requests a reportanalyzing the portion of the overhead line arrangement, which mayinclude certain support structures. In one embodiment, the supportstructures comprise poles 10, the structure of which is shownschematically in FIG. 1(b). The poles 10 generally may be described interms of three distinct components, not all of which are necessarilyincluded in a given structure: a central member 16, a crossarm 18, andan insulator 20. The central member 16 is embedded approximatelyvertically in the ground, with the crossarms 18 positioned approximatelyperpendicular to the central member 16. The insulators 20 are affixed tothe crossarms 18, with lines 22 suspended in a catenary between poles 10at the insulators 20.

[0032] In some embodiments, the central members 16 are generallyfabricated from an electrically insulative material such as wood orfiberglass. The crossarms 18 are generally fabricated from the samematerial as the central members 16, although this is not a requirementfor the invention. The insulators 20 are generally fabricated fromrubber, fiberglass, ceramic, or porcelain, all of which behave aselectrically insulative material. The overhead lines 22 supported by thesupport structures may comprise electrically conductive lines and/orstatic lines. In some embodiments, the electrically conductive lines arebare conductive lines, although in other embodiments they may compriseinsulated cables and/or bunched cables. Bunched cables typically includea plurality of single cored unarmored cables laid around aweight-carrying conductor.

[0033] The dispatcher collects system information in the form ofinspection data 110. Such inspection data 110 may be provided by theclient or obtained from other sources to identify the portion of theoverhead-line arrangement to be analyzed, including an identification ofany specific poles 10 or other support structures. The inspection data110 may also identify the environment in which the portion of theoverhead-line arrangement is included by specifying, among otherinformation, maps of the region, information identifying any linecrossovers that may exist proximate the poles 10, and informationidentifying zones where the inspection vehicle 12 (not shown in FIG.1(a)) is excluded, such as no-fly zones in those embodiments where theinspection vehicle 12 is an aircraft. In the United States, flight-plandata may be obtained from such sources as the Federal AviationAdministration (FAA) or the Aircraft Owners and Pilots Association(AOPA).

[0034] Relevant inspection data 110 are provided by the dispatcher 100to an analysis system 120, which may perform various functions asnecessary in the system and as described in greater detail below. Aspart of one such function, the analysis system 120 combines inspectiondata 110 with other data relevant for formulating an inspection plan135. Such other data may also be provided by the dispatcher 100 or maybe obtained directly from another source. One example of such relevantother data shown in FIG. 1(a) as being obtained directly from anexternal source is weather data 150 describing the existing and/orexpected weather conditions in the region to be analyzed. The inventionencompasses the use of other data sources relevant to the formulation ofan inspection plan 135, such as the locations of hotels, the locationsof rental-car companies, the layouts of nearby airports, and others asmay occur to those of skill in the art.

[0035] In this aspect of the invention, the analysis system 120 acts asa module that uses such information sources to formulate the inspectionplan 135. In embodiments using an aircraft as the inspection vehicle 12,the inspection plan 135 may be equivalent to a flight plan for theaircraft. The inspection plan 135 includes such features as a proposedinspection route, including starting points, end points, possible fuelstops, and a list of known possible hazards to the vehicle 12 such asline crossovers or antennae. In addition, the inspection plan 135 mayinclude one or more alternative routes to be followed by the inspectionvehicle 12 in the event some barrier to completing the proposedinspection route is encountered. The analysis system 120 may alsoprovide digital system maps 130 and/or a weather briefing 125, each ofwhich may additionally be included in the inspection plan 135. Theinspection plan 135 may also include other relevant informationcommunicated by the analysis system 120 that may be useful during theinspection.

[0036] The inspection is performed by navigating the inspection vehicle12 in the vicinity of the poles 10, such as shown in greater detail inFIG. 2 (described below). The inspection vehicle 12 is occupied by aninspection crew 145 which obtains information describing the inspectionplan 135 via a satellite link 140 or equivalent communications device.The inspection crew 145 may obtain any of the additional informationdescribed above as necessary or desired during its actual navigationaround the poles.

[0037] As the inspection vehicle 12 is navigated in the region of thepoles 10, it performs radar cross-section measurements, described indetail below, collecting signal data that are then provided to theanalysis system 120. Such signal data may be provided via the satellitelink 140, although alternative methods for providing such data arewithin the scope of the invention, some of which are described furtherbelow. The analysis system 120 uses the received signal data to generatea final report 115, which provides information in summary formatidentifying the potential anomalies in the poles 10 detected by thesystem. The final report 115 is communicated back to the dispatcher 100,who may review it and forward it to the client 105 for action, such asmaking a determination of whether the reported potential anomalieswarrant replacement of any of the poles 10.

[0038] While FIG. 1(a) and the above description depict a singleanalysis system 120 and a single satellite link 140, it will beunderstood that the multiple functions performed by these elements ofthe system may alternatively be performed by equivalent multipleelements without exceeding the scope of the invention.

[0039] Examples of the types of geometrical configurations that may beanalyzed are provided in FIGS. 1(c)-1(f). The simplest features of thegeometrical configurations are illustrated with FIG. 1(c), which showsan overhead line 22 suspended between two poles 10. The weight of theoverhead line 22 causes it to sag in a characteristic catenary shape,with the maximal sag from the points of suspension occurring midwaybetween the poles 10. The distance denoted d_(ls) is thus referred to asthe “line sag.” The line sag is of interest because the level of currentthat may be carried by the overhead line 22 is limited by the proximityof the line 22 to the ground and/or other lines. The permissible levelof current is influenced by numerous factors in addition to the linesag, including wind levels, ambient temperature, air density, airviscosity, and air conductivity.

[0040] A generally accepted method for determining permissible currentlevels in light of these and other factors is set forth in the IEEE 738standard. This method correlates load levels with line ampacity, whichis defined as the current a conductor can carry continuously underconditions of use without exceeding a temperature rating. Permissibleload levels are usually determined from historical weather data for thelocation of specific overhead lines. A variety of commercially availablesoftware packages exist for calculating ratings for specific seasons andeven time-of-day static ratings. In order to ensure compliance, thesestatic load ratings are often calculated on the basis of the worstambient conditions, which typically correspond to the highest summertemperatures when the lines 22 heat up and sag further under highelectrical loads. Precise measurements of actual line sag obtained withembodiments of the invention thus permit the recovery of additional loadcapacity of the line 22. For example, if a given line has a load ratingfor a particular line sag, but the actual line sag is less, the loadrating may be increased. Even relatively modest differences in line-sagdeterminations may result in substantial recoveries of load capacity.

[0041] In FIG. 1(c), the line sag d_(ls) may be viewed as a surrogatefor distance δ, which represents the minimal distance between the line22 and the ground 25. The flat ground of FIG. 1(c) is, however, somewhatidealized. More realistically, the ground is likely to have somevariation, such as shown schematically in FIG. 1(d) and/or to have somevegetation 24 that may be relatively tall, as shown schematically inFIG. 1(e). In these instances, the line sag d_(ls) by itself may not bethe most relevant parameter in determining the precise load capacity ofthe line. Instead, the minimal distance δ may be used, and this minimummay occur at points other than midway between the poles 10, as bothFIGS. 1(d) and 1(e) illustrate.

[0042] Furthermore, in more complex line arrangements, the minimaldistance δ that is relevant in defining load capacity may be withanother line rather than with the ground. This possibility isillustrated generally in FIG. 1(f), which shows two lines 22-1 and 22-2that may be considered geometrically as having a skew arrangement. Thefirst line 22-1 is supported by shorter poles 10-1 and 10-2, and has aminimal separation δ₁ from the ground. The second line 22-2 is supportedby taller poles 10-3 and 10-4 and has a minimal separation δ₂ from thefirst line 22-1. In this geometry, an accurate determination of theminimal separations δ₁ and δ₂ resulting from the respective line sags oflines 22-1 and 22-2 may permit the application of greater load levels toone or both of the lines.

[0043] A common factor that characterizes the geometric arrangementsdiscussed in connection with FIGS. 1(c)-1(f) is that they may beexpressed in terms of a relationship between an overhead line and areference object. In many instances, the reference object is the groundor a level of growth above the ground and the relationship is expressedin terms of the minimal separation parameter δ. In other instances, thereference object is another overhead line with the relationship alsobeing expressed in terms of a minimal separation parameter δ.

[0044] These geometries are purely exemplary and even more complexgeometrical arrangements may be analyzed with the invention as describedbelow, permitting adjustments in load levels applied to overhead linesin those arrangements. Also, while the geometries of these linearrangements have been described in terms of lines supported by poles,it should be understood that the geometrical aspects of the inventionare not limited to the use of poles as support. In other embodiments,lines may be supported with other support structures, such as pylons orequivalent structures.

[0045] 2. Data Collection

[0046] Generally, the navigation path taken by the inspection vehicle 12to collect data may be any path suitable for collecting the requireddata, although this may differ depending on particular applications.First, an example of the navigation path for collecting data suitablefor analyzing the poles is shown in FIG. 2, in which the inspectionvehicle 12 is depicted as a helicopter. Part (a) of FIG. 2 shows a topview of one possible navigational path that may be followed as radarmeasurements are made. In this example, the inspection vehicle 12follows an inspection path 202 approximately parallel to a locus definedby pole positions. A different navigation path may be preferred inapplications where a geometrical relationship, such as a geometry of theoverhead lines, is to be determined. In one such embodiment, thenavigation path for such applications comprises a path substantiallyabove the overhead lines.

[0047] For the example shown in FIG. 2, individual poles 10 areseparated by approximately 200 feet, a separation that is typical forutility poles, but the invention readily accommodates any poleseparation. When the inspection vehicle detects a potential anomaly inone of the poles 10, it may deviate from the inspection path 202 tofollow a verification path 204, which may include doubling back around aset of poles 10, ultimately rejoining the original inspection path toproceed to other as-yet-unexamined poles 10. While following theverification path 204, additional radar cross-section measurements areperformed from different orientations with respect to an individualpole, thereby providing supplementary data from which a more accuratecharacterization of the potential anomaly can be made. In certaininstances, the verification path 204 includes a change in relativeheight of the navigation vehicle 12, as may be appropriate in obtainingsupplementary data used to characterize crossarms on the pole 10.

[0048] The orientation of the navigation vehicle 12 with respect to anindividual pole 10 as it moves along the inspection path 202 is shownschematically in FIG. 2(b). The various distances in the arrangement areintended to be exemplary since other orientations may be used asappropriate to obtain supplementary data. In the illustratedorientation, with a pole having a height h_(p) of approximately 60 feet,the inspection vehicle 12 may be positioned at a height of about 500feet. At such a height, with a distance from the pole 10 of about 100feet, the slant range r_(s) between the inspection vehicle 12 and thepole 10 may be kept between about 135 and 550 feet, with a depressionangle θ between about 30° and 80°. The underground portion 10 of thepole 10 is preferably examined with radar signals that propagate throughthe material of the pole 10 without propagating through the grounditself. Identification of anomalies with such an arrangement requires nocorrection for the variety of electromagnetic speeds that may exist inthe ground, depending specifically on the composition of the groundwhere the pole 10 is located.

[0049] An example of a radar workstation that may be configured withinan inspection vehicle 12 is shown in FIG. 3. The particularconfiguration illustrated is appropriate, for example, for a helicoptersuch as an MD Explorer 902 or a Bell Textron 212, 412, or 427helicopter. The forward compartment of the vehicle includes seatpositions 322 and 324 for a pilot and copilot, who navigate theinspection vehicle 12 along the inspection and verification paths 202and 204. Such navigation is performed in accordance with instructionsfrom an inspection technician 146 (not shown in FIG. 3) occupying seat320 in a passenger compartment 302 of the inspection vehicle 12. Thepilot, copilot, and inspection technician may constitute the inspectioncrew 145. The inspection technician 146 is equipped with an inspectionstation 304 from which he monitors results of the inspection on outputinteraction devices 306, 308, and 310, shown in the exemplary embodimentas computer screens, and issues instructions through input interactiondevices 314 and 315, shown in the exemplary embodiment as a keyboard andmouse.

[0050] The interior of the passenger compartment is additionallyequipped with various analytical devices and instruments, which may bepositioned in locations designated generally by reference numeral 312.The illustration shows one arrangement that may be used for includingsix individual pieces of equipment. For particular applications, variouscomponents may be substituted and the configuration changed. In oneembodiment, the equipment includes the following, the operationalinterconnection of which is shown in FIG. 4: (1) a radar cross-sectionsubsystem 410 including an antenna and associated hardware forpropagating and receiving radar signals; (2) a laser pointing andmeasuring subsystem 430; (3) a differential global-positioning subsystem(GPS) 440; (4) one or more central processing units (CPUs) 450 forexecuting software as necessary to operate the various subsystems incombination; (5) a target recognition subsystem 460; and (6) adata-storage subsystem 470 for storing relevant data as needed tooperate the various subsystems in combination. In addition, theinspection vehicle 12 may include peripheral components used to insureproper and adequate functioning of the equipment 312. Such peripheralcomponents may include, among others, stabilization platforms for theradar subsystem antenna and laser, power conversion transformers toconvert from direct to alternating current (e.g., 24 V dc to 120 V ac),and battery backups as needed.

[0051] The interconnection of these various subsystems is shown inblock-diagram form in FIG. 4. The figure is divided into three primarysets: analysis elements 425, subsystem elements 465, and analysisfunctions 495. The analysis elements include the inspection technician146, the Knowledgeable Observation Analysis-Linked Advisory System(KOALAS) 480, and a remote database 122 accessible by the fixed remoteanalysis system 120. Three functions performed as the inspection vehicle12 follows the navigation path 202 to analyze the support structures inthe illustrated embodiment include: (1) focussing 492 relevant subsystemelements on the individual structures to be analyzed, such as thesupport structures; (2) extracting 494 features from each of therelevant structures; and (3) correlating 496 the location of thosefeatures both relatively with respect to the structures and absolutelywith respect to ground position. When geometric information is to becollected, such as to define a geometry of the supported lines, thefunctions performed are similar, although a geometric relationship maybe determined from compressed one-dimensional range data as a functionof data-collection time.

[0052] The inspection technician 146 interacts with the KOALAS system480 through the CPU subsystem(s) 450 to control the subsystems 465 toperform such functions. For example, during a passage of the inspectionvehicle 12 along the navigation path 202, the KOALAS system 480activates the target recognition subsystem 460, which may consist of agimbal-mounted stabilized CCD color camera or a 3-5 μm infrared thermalcamera, for example. The target recognition system is configured toidentify the structures, i.e. poles and/or lines, to be analyzed. Incertain embodiments, it is additionally configured to identifyindividual components of the structures, such as insulators on polecrossarms, and to localize the position of such components relative tothe structures. Information provided by the target recognition subsystemis used to steer the radar antenna in the appropriate direction and tocapture images of the pole structure for later use in data analysis.

[0053] Information detected by the target recognition system 460 isrelayed back to the KOALAS system 480, where it can be accessed by theinspection technician 146 for modification as may be necessary. TheKOALAS system 480, in conjunction with the inspection technician 146uses that information to steer the radar antenna in a direction towardsthe pole. At the same time, the laser subsystem 430 is used to reflectcoherent light off the structure to provide pertinent feedback data. Thefeedback data are used to provide the physical dimensions of each polestructure, including any cross arms that it may possess. Reflected laserlight is also used to determine offset height and distances of eachstructure for calculation feedback to the differential GPS subsystem440. The latitude and longitude positions of the inspection vehicle 12are known from the GPS subsystem 440. With the height and distanceinformation for each of the poles provided by the laser subsystem 430,the KOALAS system 480 performs the step of correlating positions 496 andthereby calculates the latitude and longitude positions of each polestudied for unique identification of those poles in the final report115.

[0054] In some embodiments, two radar schemes may be used inconjunction. In one embodiment, both radar schemes are contained in theradar subsystem 410. For example, FIG. 4 shows a pulse compression radarsubsystem 420 as an active component of the radar subsystem 410.Generally, the radar cross-section subsystem 410 uses a technique inwhich interferometric techniques are applied to account for the motionof the inspection vehicle 12 along the navigation path 202, thereby alsoincreasing the effective spatial resolution of the system. Incombination with measurements of reflected coherent light by the lasersubsystem 430, the step of focussing on an individual pole 492 isaccomplished. The pulse compression radar subsystem 420 uses a techniquein which short radar pulses are modulated by long ones, therebypermitting improved range resolution by removing frequency and phasemodulations. The information thus obtained is used to perform the stepof extracting features that describe the condition of the pole,including identification of possible anomalies. The physical arrangementof the various signals that are used may be understood more clearly withreference to FIG. 5, which shows a top view in part (a) and a side viewin part (b). As the inspection vehicle 12 moves along navigation path202, signals are transmitted from a rotatable nose mount 530. Forexample, the radar cross-section signal 510 (long-dashed ———) istransmitted continuously as the inspection vehicle 12 follows thenavigation path 202. The radar cross-section subsystem 410 sends out abroad band pulse that is compressed upon reception. This signal is alsointegrated into the subsequent analysis. Thus, in FIG. 5(a), the pulsecompression radar signal 515 is shown as a short-dashed line(-----------), its frequency differing from the broad band pulsefrequency. The target recognition signal 520, which may be an infraredsignal, is shown as a dotted line (• • • • • •). Finally, the distanceto a pole, its physical dimensions, and overall shape are determined byreflection off the pole of a coherent laser signal 525, which is shownas a solid line (z,900 ).

[0055] After the data have been captured and stored onboard in the datastorage system 470, a preliminary data reduction may be used to filternoise and thereby control the amount of data captured. Without suchpreliminary data reduction, approximately one terabyte of information iscollected during a typical six-hour inspection day. The filtered dataare transmitted to the analysis system 120 for more complete processing.Such data may be provided to the analysis system 120 in different ways.In one embodiment, data is written to a magnetic or optical recordingmedium, such as a CD or tape, and is physically transported to theanalysis system 120. In another embodiment, the satellite link 140(shown in FIG. 1) is used to transmit data. In one embodiment, theon-board KOALAS system 480 includes sufficient software to make apreliminary estimate of the structural integrity of the pole. Suchsoftware is a subset of the software described below used by the fixedremote analysis system 120 in its more detailed analysis, but permits animmediate evaluation of whether there is a strong likelihood that thepole is in catastrophic condition and in imminent danger of fallingover. The results of such a preliminary analysis may be provided to theinspection technician 146 in the form of a red or green light, forexample. Under such circumstances, the inspection technician 146 maymake a determination of whether the entire structure was captured foranalysis or whether a return inspection may be necessary.

[0056] In one embodiment, the following information is provided for useby the inspection technician 146 on the output interaction devices 306,308, and 310. On a first of the devices 310 is displayed a moving map,indicating the present position of the inspection vehicle 12. On asecond of the devices 306 is displayed identification information forthe particular pole then under study. Such information includes itsphysical dimensions, latitude and longitude positions, and anyidentifying number assigned to it by the client. On a third of thedevices 308 is displayed preliminary results of the radar analysis,permitting the inspection technician to decide whether to makeadditional measurements from different angular positions or to proceedalong the navigation path.

[0057] 3. Data Analysis

[0058] The radar measurement system makes use of interferometricanalyses to improve resolution, with measurements being taken atintervals as the inspection vehicle 12 moves along the navigation path202. The resolution characteristics of the combined broad band and pulsecompression modes may be understood by considering an analysis using acylindrical coordinate system such as shown in FIG. 6. A cylindricalcoordinate system naturally matches side-looking radar operations. Inthe figure, the inspection vehicle 12 at point V makes a measurement ofa radar signal reflected from point P. The position of P is defined bythe coordinates (r_(s), φ, z), with r_(s) being the slant range, φ beingthe look angle, and z being the azimuth (i.e. the distance betweennavigation path 202 and the nadir 203 projected on the surface of theearth).

[0059] For a radar system transmitting electromagnetic pulses of timeduration τ, the sensor range resolution is Δr=cτ/2≈c/2Δƒ, where the timeduration τ is approximately the inverse of the pulse bandwidth Δƒ Use ofa pulse compression ranging mode permits improved resolution by usingmodulated pulses. Thus, in one embodiment a chirp pulse is used,although other modulations may be used in alternative embodiments. Thetime dependence of the chirp pulse includes modulation with arectangular pulse rect[t/τ] of duration τ:

A _(i)(t)=e ^(i(ωt+αt) ² _(/2))rect(t/τ),

[0060] where ω=2πƒ is the angular frequency associated with carrierfrequency ƒ and α is the chirp rate related to the pulse bandwidth byατ=2πΔƒ. Without loss of generality, in the cylindrical coordinatesystem with a radar platform moving along the navigation path 202 andlocalized at z=0, and a target lying at P (r_(s), φ, 0) in the planeorthogonal to navigation path 202, the backscattered signal may beexpressed as$A = {{\exp \left\lbrack {{- \frac{}{2}}\left( {\frac{2r}{c} + \left( {\alpha \left( {t - \frac{2r}{c}} \right)} \right)^{2}} \right)} \right\rbrack}{{{rect}\left\lbrack \frac{t - {2{r/c}}}{\tau} \right\rbrack}.}}$

[0061] Processing of the received waveform is performed by convolutionwith a range reference function${{g\left( {{ct}/2} \right)} = {{\exp \left\lbrack {{- \frac{\quad {\alpha\tau}^{2}}{2}}\left( \frac{ct}{2} \right)^{2}} \right\rbrack}{{rect}\left\lbrack \frac{ct}{2} \right\rbrack}}},$

[0062] resulting in${{\hat{A}\left( {{ct}/2} \right)} = {^{- {{({2\omega \quad {r/c}})}}}{{rect}\left\lbrack \frac{{{ct}/2} - r}{c\quad \tau} \right\rbrack}\frac{\sin \left\lbrack {\frac{\alpha\tau}{c}\left( {{{ct}/2} - r} \right)\left( \left. {1 -} \middle| {\frac{2}{c\quad \tau}\left( {{{ct}/2} - r} \right)} \right| \right)} \right\rbrack}{\frac{\alpha\tau}{c}\left( {{{ct}/2} - r} \right)}}},$

[0063] which for ct/2−r□ cτ can be written${{\hat{A}\left( {{ct}/2} \right)} = {^{{- 4}\pi \quad {/\lambda}}\sin \quad {c\left( \frac{\pi \left( {{{ct}/2} - r} \right)}{\Delta \quad r} \right)}}},$

[0064] where λ is the wavelength associated with the carrier frequency.For a continuous distribution of scatterers described by a reflectivitypattern γ(r), the received pattern is given by${{\hat{\gamma}\left( {{ct}/2} \right)} = {{\int{{r}\quad {\gamma (r)}{\hat{A}\left( {{{ct}/2} - r} \right)}}} = {\int{{r}\quad {\gamma (r)}^{{- 4}\pi \quad {r/\lambda}}\sin \quad {c\left( \frac{\pi \left( {{{ct}/2} - r} \right)}{\Delta \quad r} \right)}}}}},$

[0065] with resolution of two points r₁ and r₂ being possible for|r₁-r₂|≧Δr.

[0066] The azimuthal resolution is dictated by the constraint that twopoints at a given range not be within the radar beam at the same time.Accordingly, the azimuthal resolution Δz is related to the radarbeamwidth by the relation Δz≈rλ/L, where r is the slant range and L isthe effective antenna dimension along the azimuthal direction, i.e.along the navigation direction 202 in the configuration illustrated inFIG. 6. In the radar cross-section measurement system used inembodiments of the invention, the effective antenna dimension isincreased by the motion of the inspection vehicle 12 and by coherentlycombining the backscattered echoes received and recorded along thenavigation path 202.

[0067] Thus, for 2N+1 equally spaced positions of the antenna, locatedat V_(n)(x_(n)=nd, r=0), and a point target P (r_(s),φ, 0), andisotropic radiation by the antenna within its beam width to provide anilluminated patch X=λr/L, the azimuthal-dependent part of thebackscattered signal is given by

A(nd)=e ^(−i(2π/λr)(nd)) ² .

[0068] In deriving this result, the expression

{square root}{square root over (r ²+(nd)²)}≈r+(nd)²/2r

[0069] has been used. The received signal is processed by summing overall antenna positions and convolving with the azimuthal referencefunction

g(nd)≈e ^(i(2r/λr)(nd)) ²

[0070] to give${\hat{A}({nd})} = {{\sum\limits_{k = {- N}}^{N}{^{{- {{({2\pi \quad {d^{2}/\lambda}\quad r})}}}k^{2}}^{{{({2\pi \quad {d^{2}/\lambda}\quad r})}}{({n - k})}^{2}}}} \approx {\frac{\sin \left( {\frac{2\pi \quad {Xd}}{\lambda \quad r}n} \right)}{\sin \left( {\frac{2\pi \quad d^{2}}{\lambda \quad r}n} \right)}{\left( {{nd}\quad \bullet \quad X} \right).}}}$

[0071] As for the range results, the image of a point target is spreadout. In the neighborhood of the target position at z=0,

Â(nd)≈sinc(πnd/Δz),

[0072] so that a distributed target is accounted for by superpositionaccording to the reflectivity pattern in the azimuthal direction γ (z):

{circumflex over (γ)}(nd)=∫dzγ(z)Â(nd−z)=∫dzγ(z)sinc[π(nd−z)/Δz],

[0073] where the azimuthal resolution is Δz=L/2. Because the spatialbandwidth of estimated reflectivity y is determined by the sinc functionto be 1/Δz, the processed signal for any position along the navigationpath 202 is determined by sampling interpolation:

{circumflex over(γ)}(z)=Σγ(nd)sinc[π(z−nd)/Δz]=∫dz′γ(z′)sinc[π(z−z′)/Δz].

[0074] Combining the range and azimuthal results provides the followingoverall image expression for radar signals reflected off an objecthaving a two-dimensional reflectivity pattern γ (z,r):

{circumflex over (γ)}(z,r)=e ^(−i(2ωr/c))∫∫dz′dr′γ(z,r)sinc[π(z−z′)/Δz]sinc[π(r−r′)/Δr].

[0075] As noted, such analysis then provides a resolution capability forthe radar system of Δr in the range direction and of Δz in the azimuthaldirection.

[0076] a. Anomalies in Support Structures

[0077] A detailed overview of the analytical processing of the collecteddata is provided in FIG. 7. The various forms of data collected with theinvestigation vehicle 12, including radar cross-section measurement data710, pulse compression radar data 720, laser data 730, targetrecognition data 730, and perhaps others, are subjected to a signalprocessing step 740 such as described in detail above. The various dataare subject to data fusion 742, which is a method for combining resultsto increase the confidence level of the results presented in the finalreport 115. As an illustration, when the system makes a determinationthat characterizes a feature in a pole as an anomaly, the reliability ofthe determination is increased by calculating the product ofprobabilities from different sources. For example if p_(k) is theprobability that a given feature is an anomaly based on results fromtechnique k, then the probability P that the feature is anomalous basedon the use of multiple techniques is

P=1−Π(1−p _(k))

[0078] The assignments of whether features in the structures areanomalous is performed in various embodiments at step 744 with anevaluation system that has been trained to discriminate between normaland anomalous structure according to the results of the measurements,such as with an expert system or neural network configuration. Such anevaluation system may rely on knowledge of the characteristics expectedin normal or anomalous insulative materials as stored in database 122,the generation of which is further described below. For example, theexpert system will have stored the density characteristics that definewhether features are normal or anomalous and will have stored radarscattering signals that correspond to such densities.

[0079] The radar signals reflected from a particular pole 10 may beanalyzed to identify, for example, density characteristics of the pole.Information characterizing the interior structure of the insulativematerial used to fabricate a particular component of the pole may beobtained by using radar signals having a frequency that penetrates thatinsulative material. For example, structures that are known to befabricated from rubber may be studied with radar signals using infraredor x-ray frequencies. In one embodiment, radar signals that aretransparent to the different materials that may be used to fabricatepoles are used, including wood, rubber, ceramic, porcelain, andfiberglass. An appropriate frequency range for such studies is between360 MHz and 8 GHz. In one embodiment, a frequency between 2 GHz and 6GHz is used. Defects within the individual structures may be manifestedby density changes or by the change in reflective characteristics thatresult from the defect. Thus, a void within a wooden structure, such asthe central member or crossarm, causes a change in density that may berecognized as described below. A crack within an insulator that fillswith water or metal has changed reflective properties that are evidentat these radar frequencies.

[0080] In addition, phase shifts resulting from the different refractiveeffects of the insulative material and air through which the radarsignals are propagated permits resolution of features and theirpositions within the insulative material. The analysis is illustrated inFIG. 8, in which the pole 10 is shown schematically as including a polesurface 782 and a series of planes 786 throughout the pole. The pole issubdivided into a plurality of individual cells 788 for individualcharacterization.

[0081] As the inspection vehicle 12 (not shown in FIG. 8) moves alongnavigation path 202, the radar signal for a particular cell 788-1 isfirst sensed at time t₁ and last sensed at time t₂. There are twofocussing functions that are used to define the particular cell 788-1.First, a planar coordinate position, shown in Cartesian coordinates (x,y) in the figure for convenience, causes a first phase shift Δψ₂, thatvaries with the motion of the inspection vehicle 12. Second, refractiveeffects associated with the depth of the particular cell 788-1 withinthe pole 10 cause a second phase shift Δψ₂, which remains uniform withthe motion of the inspection vehicle 12. Focussing for the planarcoordinate position is a straightforward phase correction that accountsfor path length differences between a current position of the inspectionvehicle 12 and the closest approach of the inspection vehicle 12. Depthfocussing is accomplished by using an insulative-material refractivepropagation model, such as a wood refractive propagation model incertain embodiments, to determine the effective path length differencebetween the pole surface 782 and the particular plane 786 within thepole, including the propagation delay that results from the differentindex of refraction in the insulative material.

[0082] Such analysis can thus provide, for example, a relative measureof the density distribution of the insulative material throughout acomponent of the pole. By recognizing in particular closed volumeswithin the pole where the density is consistently less than the meandensity of that region, structural anomalies are identified, togetherwith their location. For example, a potential anomaly within the centralmember or a crossarm is identified by its density being less that theaverage density of the central member or crossarm in that region. Sincethe comparison is of a relative measure of the density, the method canfunction independent of knowing precisely what type of insulativematerial any particular component of the pole is made of.

[0083] The process of drawing these conclusions by performing the modelcomparison 744 is essentially a pattern-recognition algorithm beingconducted by the trained evaluation system. In any specificimplementation of such a pattern-recognition algorithm, it is beneficialto ensure that the trained evaluation system is making reliabledeterminations. This may be done by preliminary training of theevaluation system with an appropriate set of certifiable data thataccounts for relevant factors in making the determinations, which isthen encoded before the system is used to evaluate real data. Forexample, measurements may be performed on a number of poles, some ofwhich are known to contain anomalies. Based on the identification ofthese anomalies, this information is used to train the evaluationsystem's pattern recognition algorithm. In particular, the preliminarytraining may include a pole strength assessment (perhaps expressed as apercentage probability that the pole will fail within a certain time asa result of the anomaly) determined from a complete analysis of the poleexternal from the radar measurements.

[0084] Using artificial-intelligence techniques, the results ofsubsequent tests are used continually to perform refinement of the modelused in making the structural determinations (step 748). For example, inone embodiment, a neural net is used to make the structuraldeterminations. A typical neural network includes a plurality of nodes,each of which has a weight value associated with it. The networkincludes an input layer having a plurality of input nodes and an outputlayer having a plurality of output nodes, with at least one layertherebetween. In this example, the input nodes receive the data providedby the various sensor measurements and the output nodes generate aninterpretation designation. The interpretation designation may be asimple binary indication, such as described above, that a given pole isimminently likely to collapse or not. Alternatively, the interpretationdesignation may be a numerical percentage reflecting the pole strengthassessment. In other words, given an input comprising the sensormeasurements, the input is combined (added, multiplied, subtracted, etc.in a variety of combinations and iterations depending upon how theneural network is initially organized), and then the interpretation isgenerated accordingly.

[0085] In order to train the neural net, the output values are comparedagainst the correct interpretation with some known samples. If theoutput value is incorrect when compared against such a testinterpretation, the neural net modifies itself to arrive at the correctoutput value. This is achieved by connecting or disconnecting certainnodes and/or adjusting the weight values of the nodes during thetraining through a plurality of iterations. Once the training iscompleted, the resulting layer/node configuration and correspondingweights represents a trained neural net. The trained neural net is thenready to receive unknown sensor data and designate certain pole regionsas containing anomalies. Classical neural nets include Kohonen nets,feed-forward nets, and back-propagation nets. The different neural netshave different methods of adjusting the weights and organizing therespective neural net during the training process.

[0086] The analysis system may make use of other methods for makinginsulative-structure anomaly assignments on the basis of the sensordata. Such methods may be broadly categorized as falling into one of twoclasses. In the first class, the method begins with an initialapproximation that is progressively improved using comparison feedback(step 746). For example, for a given pole, the analysis system beginswith an initial structural estimate for the pole. The sensor data thatwould result from a pole with those precise characteristics iscalculated and compared with the actual sensor data. From such acomparison, the estimated structural characteristics for the pole arerefined. The process proceeds iteratively, with the estimated polestructure being modified at each step to reproduce the measured sensordata more closely. When the difference between the measured sensor dataand the calculated sensor data is less than a predetermined threshold,the process is deemed to have converged and the final report 115 isissued.

[0087] In the second class of methods, the system is permitted to varyessentially randomly and individual pole-characteristic representationsthat develop during the process are evaluated to determine which bestreproduces the measured sensor data. One example of such a method is agenetic algorithm. The genetic algorithm is a model of machine learningthat derives its behavior in an attempt to mimic evolution in nature.This is done by generating a population of “individuals,” i.e.pole-characteristic representations, represented by “chromosomes,” inessence a set of character strings that are analogous to the base-fourchromosomes of DNA. The individuals in the population then go through aprocess simulated “evolution.” The genetic algorithm is widely used inoptimization problems in which the character string of the chromosomecan be used to encode the values for the different parameters beingoptimized. In practice, therefore, an array of bits or characters torepresent the chromosomes, in this case the position and sizes ofanomalies in the insulative structures of a pole, is provided; then, bitmanipulation operations allow the implementation of crossover, mutation,and other operations.

[0088] When the genetic algorithm is implemented, it is trained in amanner that may involve the following cycle: the fitness of allindividuals in the population is first evaluated; then, a new populationis created by performing operations such as crossover,fitness-proportionate reproduction, and mutation on the individualswhose fitness has just been measured; finally, the old population isdiscarded and iteration is performed with the new population. Oneiteration of this loop is referred to as a generation. According toembodiments of the present invention, a number of randomly generatedpoles with various anomalies may be used as the initial input. Thispopulation of poles is then permitted to evolve as described above, witheach individual pole being tested at each generation to see whether itcan adequately reproduce the measured sensor data.

[0089] Still further methods that may occur to those of skill in theart, involving such techniques as simulated annealing or various fuzzylogic systems, may be used alternatively or supplementally to performthe analysis of the measured sensor data to generate the final report115.

[0090] b. Geometrical Analyses

[0091] In addition to enabling the detection of anomalies in supportstructures, the system described enables geometric analysis of theoverhead line configurations. This capability is enabled by the factthat all the features necessary for performing such geometric analysisare visible from the processed results, including the arc of theoverhead line, the ground surface, brush and other growth, etc. Thispermits a determination not only of the line sag itself, but also adetermination of other geometric features, such as the minimum distanceof the overhead line from the ground and/or from any growth under theline. A specific example of processed results illustrating such featuresis discussed below.

[0092] In tests performed by the inventors, it has been found possibleto process the data to make such geometric determinations in about fiveminutes or less and with a resolution better than half an inch.Moreover, the method and system described herein function without anyneed for specific reconfiguration of the overhead lines or for limitingthe time of day when the data may be collected. Such analyses thus havesignificant advantages over optically based methods for obtaininggeometric information regarding overhead lines. Such optically basedmethods generally fall into two classes. In one class, a camera is usedto sense reflections from a reflector placed on the overhead line whenan LED is illuminated near the overhead line at night. This class ofmethods is constrained by the need to place reflectors on the lines, theneed to fix detection equipment near the lines, and the need to collectdata only at night, among other difficulties. In the second class, aladar system is used to reflect a laser beam off the lines. Both theresolutions are processing times for analyzing the optical data arebelieved to be substantially greater than can be achieved with themethods and systems disclosed herein.

[0093] A further advantage of the methods and systems described hereinis the ease with which geometric analyses of overhead lines may becoupled with detection of anomalies in the structures that support them.

[0094] 4. Exemplary Results

[0095] An example of the format of the final report 115 and the type ofinformation included on it is shown in FIG. 9. The final report 115 maycomprise of a plurality of such depictions as shown in FIG. 9, one foreach pole examined, and may include information in more summary formsuch as in a table.

[0096] In the report format shown in FIG. 9, preliminary information isused to identify the name of a client 802 who commissioned theinvestigation of the pole structures and the date 804 the inspection wasperformed. Specific information identifying the individual pole for thereport may take the form of providing a pole number 806 and line name808; in this example the report is for pole 17 of 354 poles on the RioOsa—Table Mountain 69kV line. The specific location 810 of the pole,determined as described above, is provided in a format specifyinglongitude and latitude to facilitate identification of the pole shouldremedial measures be warranted and/or desired. The report includesinformation reporting the results of the analysis. Such information maybe in the form of a graphic 814 showing the general size and shape ofthe pole, with an indication of where detected anomalies lie. It mayalso include a textual description 812 of the location of the anomalies,using ground level and the pole centerline as reference points. Thereport may further include a quantitative evaluation 816 of the effecton pole strength caused by the various detected anomalies. The identityof the inspection technician may also be included.

[0097] In the example shown, the system has detected three anomalies inthe pole, which has a single crossarm. The first anomaly isapproximately at ground level in the vertical pole having a size ofabout 1.3098 ft³. Based on the analysis system, using a trainedevaluation system such as an expert system or neural network, thisanomaly is estimated to reduce the strength of the pole by 35.7% fromits strength without the anomaly. The second anomaly is larger andlocated about 50 ft above ground level and the third anomaly, which issmaller, is located in the crossarm. The estimated effect of each ofthese anomalies on the strength of the pole is included in the report.This information may then be used by the client to decide whether totake corrective action based on its own criteria, such as to replace anystructure suffering from a strength reduction greater than 40%.

[0098] FIGS. 10(a) and 10(b) show radar results that respectivelyillustrate the anomaly-detection and geometric analyses enabled by theinvention. In both figures, the radar results are representedlogarithmically with decibel levels corresponding to the amplitude ofreceived signals. A color scheme displays the higher decibel levels inred and the lower decibel levels in blue. FIG. 10(a) shows two panels topermit comparison of images of a pole in the visible spectrum (in theleft panel) with images of the same pole using the radar results (in theright panel). Line 1002 is used to show the level of the ground in thetwo images, which is offset for the radar image because of the abilityof the system to detect structural details of the pole below the ground.While no anomaly is apparent in the left visible image, a defect isclearly visible in the right radar image, corresponding to the redportions of the image. The larger part of the defect is seen to be aboveground level, but there is also a part of the defect under ground level.Line 1002 is used to show the correlation in position of the larger partof the defect from the radar image with its position in the visibleimage.

[0099]FIG. 10(b) shows a radar image at a larger scale to illustrate thederivation of geometric information regarding the position and shape ofoverhead lines. The width of the image is approximately 500 feet, withthe numerical values shown on the image indicating distances in inches.The image is inverted and decibel levels 1004 are indicated explicitly.The depicted area is near the bottom of the sag for both conductor 1016and static overhead lines 1020. The nature of the lines is evident fromtheir different colors in the image, with the static lines 1020appearing in blue and the conductor lines 1016 appearing in yellow andred. There are two static lines 1020 and three 345-kV conductor lines1016, one of which is hidden behind another at the greater height (lowerin the image) but which can be seen separately at the right of theimage. The ground 1008 appears in red at the surface and diminishes indecibel level with depth. Brush 1012 growing at the surface appears inlight blue. This image illustrates the typical characteristic that theground is not flat and has some overgrowth vegetation.

[0100] The method and system are not limited in the types of overheadlines that can be identified and may therefore be used not only forconductor lines and static lines, but also for transmission lines anddistribution lines. The radar image of the overhead lines 1016 and 1020also provides sufficient information to extract all the desiredgeometric information. In some instances, this geometric information maybe a single parameter, such as the minimum distance between theconductor lines 1016 and the ground 1008. In this example, that minimumdistance is 32 feet, 7 inches. In more complex geometric arrangements,the single parameter may instead correspond to the minimum distancebetween two conductor lines. In other embodiments, the informationderived from the radar results may be used to generate a multiparameterdescription of the shape of the overhead line, such as by using acurve-fitting technique to a catenary of the form y(x)=A₀+A cosh(αx+β),where y represents the height of the line as a function of horizontaldisplacement x.

[0101] Having described several embodiments, it will be recognized bythose of skill in the art that various modifications, alternativeconstructions, and equivalents may be used without departing from thespirit of the invention. Accordingly, the above description should notbe taken as limiting the scope of the invention, which is defined in thefollowing claims.

What is claimed is:
 1. A method for characterizing an overhead line, themethod comprising: propagating a radar signal having a frequency between50 MHz and 100 GHz in a region that includes at least a portion of theoverhead line and a reference object; receiving a reflected radar signalfrom the overhead line and the reference object; and determining ageometric relationship between the overhead line and the referenceobject from the reflected radar signal.
 2. The method recited in claim 1wherein the radar signal is propagated with a radar antenna while theradar antenna is in motion.
 3. The method recited in claim 1 wherein thegeometric relationship is defined by a minimal separation between theoverhead line and the reference object.
 4. The method recited in claim 1wherein the reference object comprises a ground surface.
 5. The methodrecited in claim 1 wherein the reference object comprises a growth abovea ground surface.
 6. The method recited in claim 1 wherein the referenceobject comprises another overhead line.
 7. The method recited in claim 1wherein the overhead line comprises a conductor line.
 8. The methodrecited in claim 1 wherein the overhead line comprises an electricaldistribution line.
 9. The method recited in claim 1 wherein the overheadline comprises an electrical transmission line.
 10. The method recitedin claim 1 wherein the radar signal has a frequency between 2 and 6 GHz.11. The method recited in claim 1 wherein the reflected radar signal isfurther received from a structure supporting the overhead line, themethod further comprising determining whether the structure contains astructural anomaly from the reflected radar signal.
 12. A method forcharacterizing an overhead line, the method comprising: propagating aradar signal having a frequency between 50 MHz and 100 GHz with a radarantenna while the radar antenna is in motion; receiving a reflectedradar signal from the overhead line; and determining a line sag of theoverhead line from the reflected radar signal.
 13. The method recited inclaim 12 wherein the overhead line comprises a conductor line.
 14. Themethod recited in claim 12 wherein the overhead line comprises anelectrical distribution line.
 15. The method recited in claim 12 whereinthe overhead line comprises an electrical transmission line.
 16. Themethod recited in claim 12 wherein the reflected radar signal is furtherreceived from a structure supporting the overhead line, the methodfurther comprising determining whether the structure contains astructural anomaly from the reflected radar signal.
 17. A system forcharacterizing an overhead line, the system comprising: a radar antennaadaptable to emit and receive electromagnetic signals having a frequencybetween 50 MHz and 100 GHz; and an arrangement of at least one computersystem in communication with the radar antenna and configured to acceptinstructions from an operator and to operate the radar antenna inaccordance with the following: propagating a radar signal in a regionthat includes at least a portion of the overhead line and a referenceobject; receiving a reflected radar signal from the overhead line andthe reference object; and determining a geometric relationship betweenthe overhead line and the reference object from the reflected radarsignal.
 18. The system recited in claim 17 wherein the overhead linecomprises a conductor line.
 19. The system recited in claim 17 whereinthe overhead line comprises an electrical distribution line.
 20. Thesystem recited in claim 17 wherein the overhead line comprises anelectrical transmission line.
 21. The system recited in claim 17 whereinthe radar antenna is connected with a vehicle to propagate the radarsignal while the vehicle is in motion.
 22. The system recited in claim17 wherein the reflected radar signal is further received from astructure supporting the overhead line, the arrangement of at least onecomputer system further being configured for determining whether thestructure contains a structural anomaly from the reflected radar signal.